A. Technical Field
The present invention relates to a catalyst used for production of acrylic acid and a process for production of acrylic acid using this catalyst. Specifically, the present invention relates to: a catalyst for production of acrylic acid, which catalyst is excellent in activity, selectivity, and physical strength and the like; and a process for production of acrylic acid by subjecting acrolein to catalytic gas phase oxidation in the presence of molecular oxygen and the catalyst.
B. Background Art
As a catalyst for efficiently producing acrylic acid by catalytic gas phase oxidation of acrolein (catalyst for production of acrylic acid), there is often used a catalyst which is obtained by a process comprising the steps of: adding a liquid binder to a powder obtained from a mixed liquid of starting materials including molybdenum and vanadium as essential components; molding the resultant mixture; and then calcining the resultant molding. As to processes for producing this catalyst, various proposals have been made.
Examples of these production processes include: (1) a process comprising the steps of evaporating a mixed liquid of starting materials to dryness, adding polyvinyl alcohol, a water-absorbent resin, and water to the resultant dried powder, and then kneading and extruding the resultant mixture (for example, see patent document 1 below); (2) a process comprising the steps of spraywise drying a mixed liquid of starting materials and calcining at 400° C., and then supporting the resultant calcined mixture onto a carrier using water as a binder by a rotating drum type supporting apparatus (for example, see patent document 2 below); (3) a process comprising the steps of drying a mixed liquid of starting materials by any method of evaporation to dryness, spray drying, drum drying, and gas flow drying, calcining the resultant dried powder, and then adding propyl alcohol and water to the resultant calcined material, mixing, and then extruding the resultant mixture (for example, see patent document 3 below); (4) a process comprising the steps of spraywise drying a mixed liquid of starting materials and calcining at 400° C., and then supporting the resultant calcined mixture onto a carrier using a liquid binder including water and an organic compound having a boiling point or sublimation temperature of higher than 100° C. under normal pressure (for example, see patent document 4 below); and (5) a process comprising the steps of drying a mixed liquid of starting materials and pre-calcining at a temperature in the range of 250 to 500° C., and then supporting the resultant calcined mixture onto a carrier using such as an aqueous glycerol solution as a binder by a tumbling granulator (for example, see patent document 5 and patent document 6 below).
[Patent Document 1]    JP-A-096183/1993 (Kokai)
[Patent Document 2]    JP-A-279030/1994 (Kokai)
[Patent Document 3]    JP-A-010621/1996 (Kokai)
[Patent Document 4]    JP-A-252464/1996 (Kokai)
[Patent Document 5]    JP-A-299797/1996 (Kokai)
[Patent Document 6]    JP-A-079408/2001 (Kokai)
However, all the catalysts for production of acrylic acid, which catalysts are obtained by the above prior processes, are still insufficient in the catalytic performances such as catalytic activity and in the physical strength of the catalysts themselves.